1. Field of the Invention
This invention relates to a device for correcting roll paper curl and a record apparatus comprising that device.
2. Description of Related Arts
In a record apparatus typified by a FAX, a printer, etc., roll paper on which recording (print) can be executed over long length is used. In recent years, as a consumer-oriented printer for realizing photo image quality, a printer that can print at silver-salt photo level using roll paper has been developed.
On the other hand, the roll paper has a characteristic different from that of a usual single sheet of paper, namely, has nature of curl left still after being unrolled because the roll paper is rolled like a roll. Thus, a disadvantage may occur in handling the roll paper after print. That is, if the roll paper is curled, the possibility that a paper jam may occur in a print process is raised and in addition, print matter cut to a predetermined length as a single sheet of paper is rounded and it becomes difficult to flatten it neatly.
To remove such curl of roll paper, for example, Japanese Patent Publication JP-56-43152A (or JP-62-3729B) proposes a device wherein one of a pair of rollers is made up of a rotatable shaft member and a circumferential member disposed on the peripheral surface of the shaft member for rotation and the shaft member is provided in a part with a decurl member projecting from the surface of the circumferential member and having a concave face fitted into a part of the surface of the other roller.
JP-07-277566A proposes a decurling device comprising a decurl roller for coming in contact with the outer face of roll paper and inverting the roller paper to the outside for removing curl of the roll paper, decurl release device for moving the decurl roller at the decurl release stop time, an urging device for urging the decurl roller by a predetermined force at the decular release operation time, and a turn roller and a guide section for clamping and transporting the decurl roller and record paper at the decular release operation time.
However, in the related arts, when the curl of roll paper is removed, the curl is forcibly corrected with the roller surface in contact with the print side of the roll paper and thus there is a possibility that the print side may be damaged, may be made dirty, or may be wrinkled.
Generally, to reliably correct the curl of roll paper, it is necessary to lessen the curvature when the roll paper is curved; however, for example, if the roll paper is thick high-image-quality print paper having a coat layer, it is feared that the roll paper cannot appropriately or smoothly pass through a curve formation section for forming the roll paper with a curve condition because of the effect of the rigidity of the roll paper.
On the other hand, if the curl correction degree is stronger than the original roller paper curl, the roll paper is curved (overdecurled) in an opposite direction to the original curl.
If the roll paper is thus overdecurled, for example, the following problem occurs: In an ink jet printer capable of printing on roll paper, when roll paper is rolled with the print side upside, if the roll paper is overdecurled as described above, the roll paper tip gets snagged on a paper transport passage or comes in contact with an ink jet record head (head rubbing) and appropriate print operation cannot be performed or appropriate print quality cannot be provided.